The default mode for Google driverless cars currently is yield, shutting down in the presence of any unusual aggression, but that’s not realistic in the long run. How can the autonomous vehicles “gain confidence” without sacrificing safety? From Steve Johnson at the Seattle Times:

“In 700,000 miles of navigating roads, Google’s self-driving cars have encountered just about everything — including an older woman in a motorized wheelchair flailing a broom at a duck she was chasing around the street.

Apparently perplexed and taking no chances, the vehicle stopped and refused to go farther.

Through extensive testing covering nearly every street in Mountain View, the company’s 20 or so autonomous vehicles have developed an abiding sense of caution. But Google researchers concede it will take more experience on the roads before the autos can learn to cope with every situation without becoming bewildered and shutting down, stranding passengers. When that happens now, researchers have to take the wheel and step on the gas.

One of the most surprising lessons: While hoping to make cars that are safer than those driven by people, Google has discovered its smart machines need to act a little human, especially when dealing with pushy motorists.

‘We found that we actually need to be — not aggressive — but assertive’ with the vehicles, said Nathaniel Fairfield, technical leader of a team that writes software fixes for problems uncovered during the driving tests.”